#5 - Root mean square #25
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boristane
requested changes
Jan 4, 2019
| - [mean](#mean) | ||
| - [harmonicMean](#harmonicMean) | ||
| - [geometricMean](#geometricMean) | ||
| - [rootMeanSquare](#rootMeanSquare) |
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Can you please rename the method to rms as set in #5 ?
| #### rootMeanSquare | ||
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| ```js | ||
| rootMeanSquare(arr); |
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Please rename to rms throughout all files.
| * @returns {Number} the arithmetic mean of the data array | ||
| */ | ||
| export function rootMeanSquare(arr) { | ||
| if (min(arr) === undefined) return undefined; |
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I understand what you are checking here but it is a bit counter-intuitive. It is not necessary to compute the min of the array when calculating its rms. Could you please use this check instead ?
if (!Array.isArray(arr) || arr.length === 0) return undefined;| for (let i = 0; i < arr.length; i += 1) { | ||
| arrSquareSum += arr[i] ** 2; | ||
| } | ||
| return Math.sqrt((arrSquareSum / arr.length)); |
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Although this approach solves the problem, it does not make use of previously defined methods in the library. We could use the literal definition of the rms:
- Compute the mean of the squared values of the elements of the array;
- Compute its square root if it exists.
This would give something like this:
function rms(arr) {
const xBar = mean(arr.map(elt => elt ** 2));
return xBar === undefined ? undefined : Math.sqrt(xBar);
}
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The description of root mean square may be lacking. Let me know if anything needs updating. Thanks!